Pulse width modulator for transmission solinoid.

Thread Starter

ThatOtherGuy

Joined May 30, 2016
2
Hi I am wanting to build a device to allow me to lock up the torque convertor clutch in my transmission of my Toyota Prado overriding what the trans control is telling it to do to improve its performance while towing. I have built a basic circuit that just supplies 6 volts via a load resistor to the solenoid that controls the clutch however this is a rather harsh engagement of the clutch. I'd like to build something that will replicate the pulse width modulation that the vehicles control unit does but am a little out of my depth. Can anyone offer any advice.

If someone can do this I will post some snapshots off my oscilloscope of how the transmission control unit operates the solenoid.
 
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crutschow

Joined Mar 14, 2008
25,269
Yes, we need an oscilloscope photo of the present signal to the solenoid from the control unit.
The photo need to show the detail in the PWM signal pulses.
 

jpanhalt

Joined Jan 18, 2008
10,108
You may also need some sort of protection for the ECM, as outputs are often low impedance and a high from your device during a low from the ECM might create a fault or visa versa. With your 6 V DC, were there any problems? If protection is necessary, can you use a protective diode (diode OR'd) for the signals or a logic gate (OR) to protect the ECM?

John
 

shortbus

Joined Sep 30, 2009
7,855
Locking a torque convertor clutch when the ECM/TCM is not calling for it is not a good idea. The convertor clutch unlocks to provide the torque multiplication need to keep the vehicle moving at the speed the throttle position sensor is calling for. If the clutch doesn't unlock when it is supposed to this puts too much strain on that clutch. The engineers that designed the power train did what they did for a reason. The convertors "vanes" can withstand way more torque than the convertor clutch can.
 

Thread Starter

ThatOtherGuy

Joined May 30, 2016
2
You may also need some sort of protection for the ECM, as outputs are often low impedance and a high from your device during a low from the ECM might create a fault or visa versa. With your 6 V DC, were there any problems? If protection is necessary, can you use a protective diode (diode OR'd) for the signals or a logic gate (OR) to protect the ECM?

John
The system I have uses 2 co relays to swap the solinoid to my 6 volt supply and the trans control unit to a resistor to replicate the solinoid coil being there to prevent fault codes in the system.

Locking a torque convertor clutch when the ECM/TCM is not calling for it is not a good idea. The convertor clutch unlocks to provide the torque multiplication need to keep the vehicle moving at the speed the throttle position sensor is calling for. If the clutch doesn't unlock when it is supposed to this puts too much strain on that clutch. The engineers that designed the power train did what they did for a reason. The convertors "vanes" can withstand way more torque than the convertor clutch can.
The engine has been modified to produce more torque and the converter clutch modified to withstand the increased torque. The override will only be used when there is sufficient torque in the engine to maintain road speed with out unlocking the convertor clutch and provide engine braking.
 
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